I downloaded it a few days ago now and i've been loving it. When i'm restrained from playing counterstrike this gives me the perfect online shoot them in the face expirience.
As for the little aiming problems that's happening, you do know you can lock onto a target by holding down R right? And strafe by holding down L. Both make a massive improvment to the playabilty, and after realising this I had a score ratio of at least 1:1. I've never thought a PSP shoter could ever work, especially as i've refused to touch the nub after trying to play Jr. and my hand almost falling apart, but after playing this it just seems wonderful, I can really see the final version being something I actually want to buy.
Shame about the lack of any communications though, a game like this really need a mic or something.